Digital SLR Camera Lenses - Advice Request

[Arrqh]

^^ That's a common mistake. The focal length remains the same despite the crop factor. So, the image is enlarged by that factor but the focal length and how that affects the appearance remains the same. In other words, if you move back just enough to counter the crop factor, it would look the same as a 50mm on a full frame (but closer to the subject).

Imagine the circle of light that goes through the lens. Now, the image in the light doesn't change based on the sensor in your camera. Rather, full frame and crop sensors just capture a different portion of that light without changing how the actual image in the light appears. It's difficult to explain but basically the sensor size isn't changing the information in the light from the lens.

No, that is not correct. The focal length of the lens only determines one thing, and that's the field of view. However the perspective of the image is determined by your positioning relative to the objects you're shooting. As a result, if you need to step back with a crop frame camera to get the same objects in the frame you have changed the perspective and you are no longer capturing the same image. You may have captured the same objects at the boundaries of the image but the spatial relationships will all be altered.

Therefore, if you have the exact framing and composition with your eyeballs and you then look through your 50mm on a 1.6x crop you cannot take the image of what you see. Either your field of view will be narrower, meaning you've lost the edges of your frame, or you have to take a few steps back which means the perspective of your shot has changed. That's why a 30mm is closer to a normal lens then a 30mm on a crop frame... the field of view on the image is as close as you can get to your eyes and you don't have to change the perspective by moving to get the same angle.

 

[Mr Awe]

^^ Look at it this way, the image coming through the lens is the same regardless of which sensor is in your camera. So, the 50mm lens is producing the same image, it's just cropped differently. So, agree, the cropping is different but otherwise it's the same image and the 50mm matches your eyes the best.

Mr Awe

 

[Arrqh]

Yes, I understand what you're saying, but it isn't correct. The 50mm will either cause you to get a narrower field of view then your eyes on the final image or will cause you to get a different perspective by forcing you to move your camera.

There is actually no difference between any focal length lens with a camera shot at the same position in terms of anything else other than focal length. If you took a wide angle lens and a telephoto lens, took a shot with each and then cropped the former to match the latter you would get the exact same image twice. The distortion typically associated with wide angle lenses is not due to the lens properties but due to the perspective shift caused by the placement of the camera. There's a good thread illustrating perspective control here: http://photography-on-the.net/forum/showthread.php?t=672913

So again, if the only thing that a lens controls is a field of view, the "correct" focal length to use is one where the final image matches the field of view of your eyes when shot from the same place you stood when you composed the image. And on a 1.6x crop, that is ~30mm.

 

[Mr Awe]

^^ You will move you camera, but where ever you move it to, you'll still be seeing a 50mm image that mirrors your eyes. So, you're correct, you would position yourself differently and that might change your perspective on things subtly. However, the image is still delivered to your sensor by a 50mm lens that mirrors your eyes.

I'm not saying that you perspective wouldn't be somewhat different, sure, you're in a physically different location. Just that images from a 50mm lens still mirrors your eyes even with crop sensor. The lens doesn't alter the image based on sensor type. Rather, the sensor just collects a different portion of it.

I just read the article you linked to and it is consistent with what I'm saying. Physically relocating yourself will change the perspective but you're still getting the same image through a 50 mm lens, just cropped differently. I think we're just saying the same thing but in different ways!

Mr Awe

 

[Guartho]

Personally, the 50mm f/1.8 was my first prime and after a few months I stopped using it. I found 50mm to be either too narrow or too wide for my shooting preferences. So now I own a prime on either end, a 30mm and a 100mm. If I had started out with the 1.4 that would have been $400 down the tube!

Wish I'd read this post last year. I was shooting DSLR video with a 50mm prime 1.4 borrowed from a photographer friend and I was absolutely enamored with the narrow depth of field. I bought one for myself. (Hey videographers, image stabilization is much more important to us than it is to photographers in most situations) Anyway, I find that it's just too telephoto for most of my needs and was $400 down the tubes. I really wish I had a 30mm, but I just can't justify the expenditure.

 

[Q2UnME]

Thanks all for the interesting discussion on lenses. Up until recently, all my photographic experience has been with film cameras or point-n-shoot digital cameras.

What kind of pisses me of is that I've got literally $1500 to $2000 in various SLR film lenses that cannot be used in the digital environment. I have an Olympus OM-1 and two Olympus OM-10 camera bodies, 1 @ 50mm Zukor, 1 @ 35-85mm Zukor and 1 @ 70mm-210mm lenses. Olympus was late to the DSLR party and decided not to go backward compatible with their old manual lenses, just the last generation autofocus lenses. Those "old" glass lenses are light years better than what I'm seeing in the DSLR world (without racking up some huge $$).

I've not had a whole lot of experience with Canon, but the reviews were pretty good and at 12 megapixel (jpg and raw), more than enough information for good 8"x10" or 11"x14" blow up prints. When the opportunity came up to get the DSLR camera for a good price I went for it. I'm trying to learn the settings necessary to take for control of shutter speed, F/stop, ASA (or ISO) and manual focus. I'm a little disapointed in the depth of field in some shots in the automatic settings. I'd rather manually set the f/stop and let the camera set the shutterspeed or set both the f/stop and shutter. I guess I'm just falling back on 30+ years of SLR experience. Time will tell....

Q2

 

[LitmusDragon]

Rise from your thread grave!

I'm about to come into a large sum of money and join the DSLR market. For camera I have more or less decided on Canon 60D. The longer battery life versus the rebel models is attractive to me. How is this for a lens setup? The three types of shoots I plan to do mainly are a) Live music (highest priority) b) Wildlife/birds c) Flowers, insects, small objects (narrow DOF with nice brokeh)

17-55mm USM IS f/2.8 - General walkabout lens and for shooting live music during the day or with a lot of light

50mm Prime f/1.4 - For shooting live bands in dimly lit clubs (I plan to do this often). Also for shooting flowers with a narrow DOF

70-300mm f4-5.6 USM IS - Long telephoto for birds / wildlife / outdoor music festivals with abundant light

The main concern I have is whether or not the 50mm will be too narrow a field of view on a 1.6x crop body. Still in terms of bang for the buck it's the fastest prime I am likely to get for low light. The next best choice would seem to be a Sigma 30mm f/1.4, however it's more expensive and it's not a Canon lens.

Instead of the 70-300mm I could also get the L-series 70-200 f/4 which is a bit faster and has constant aperture but NO IS so I would probably end up purchasing a monopod to go with it (increasing price slightly). I am attracted to this lens because I believe it will focus faster than the 70-300 however I don't like the idea of lugging a monopod around. Then again it is L-series glass.

Looking for the opinions of our resident DSLR experts.

 

[Mr Awe]

I have the 50mm f/1.4 and love it! Whether it's too narrow depends on how close you are to the action. I've heard great things about the 17-55mm f/2.8 and that should be pretty good in low light as well. So, I guess if you're too close for the 50mm, you can pop in the 17-55mm and crank up the ISO a bit. 2.8 still lets in a lot of light.

I don't have the 70-300mm but I do have the 70-200mm L f/4 and you can in fact get it with IS. I love this lens!! It's extremely sharp, quick focus, and the late generation IS is superb. I never use a monopod with it--mine has the IS.

Mr Awe

 

[LitmusDragon]

Thanks Mr Awe, that does help. I have heard nothing but good things about the Canon 70-200mm lenses. Now I am considering getting the 70-200 f/4 with IS as my only zoom lens (for now) and then the 50mm f/1.4 for low light. I really like the idea of prime lenses and the challenge and jump in quality they present. Then my next purchase would probably either be a 135mm prime or a 17-55 zoom if I decide that I need it. I am also considering options for 400-500mm for birding. There really are a lot of options. o_O I have read some bad things about the cheap 70-300 I was looking at in terms of build quality so I think I have decided against that one at this point. There is an L-series 70-300 as well but it's much heavier than the 70-200 f/4, I don't want my first zoom to be something huge that I'm going to regret carrying around with me.

edit:
After reading the thread again I am now considering the Sigma 30mm f/1.4 instead of the 50mm f/1.4.

 

[Mr Awe]

Let your expected use, previous shooting habits be your guide for deciding between the 30mm and the 50mm primes.

The 70-200mm L IS I've found to be very easy to carry around. No regrets there.

For birding, and wildlife in general, you often need 400mm or more. Typically, 300mm isn't quite enough. Depends on what you're shooting and how far away, of course.

I wasn't even aware of the 70-300mm L lens! It's pretty new! My next zoom will probably be the 100-400mm L.

Mr Awe

 

[LitmusDragon]

So in the end I decided on 3 lenses: 1) The 50mm f/1.4 as a really fast low-light lens for live music in clubs 2) The 70-200 f/4 with IS just because it's such an awesome lens (I'll probably use it for outdoor music festivals) 3) The kit 18-135 lens which gets pretty good reviews (and factoring in price of the kit, is only $260, a good deal I think)

I am not sure if I'll end up using the 18-135 or the 70-200 more often, but it's nice to have both options.

 

[Mr Awe]

My general, walkabout lens is the amazing 24-105 f/4 L IS USM. If I could only own 1 lens, that would be it. That'll work for the vast majority of my pictures. I would miss my other lenses, particularly the 70-200mm.

I've got the Canon 24-70mm f/2.8 L lens that is pretty good. Great image quality. I wish it had IS but it lets in a good amount of light. I don't use this one as much as I thought, though.

The Canon EF-S 10-22mm f/3.5-4.5 USM (only for cropped sensors) has great image quality. I don't use this lens a lot but when I do, I *really* need it.

Anyway, it sounds like you've got a good set of lenses! Becareful, I find it's addicting! I'm drooling over the new Canon 100mm L macro lens. Macro shots look like fun! I also want the 100-400mm L lens when I really need that extra reach!

Mr Awe